With growing awareness for environmental problems in recent years, electronic devices that operate with less power consumption have been spread rapidly. For instance, in a process of generating power necessary to drive an electronic device, reduction of power lost in the power supply device is a major subject from the viewpoint of realizing power saving. As a method for reducing this power loss, a feedback method is known. In other words, the method detects a state of power output from the power supply device. The method controls output power in accordance with the detected state of power. When the feedback method is adopted, the power supply device can optimize a power conversion efficiency (hereinafter, in the present application, referred to simply as “conversion efficiency”) upon conversion from DC power to AC power, for example. As existing related technologies, there are, for example, technologies disclosed in PTL 1 and PTL 2, in addition to the above-described feedback method.
PTL 1 discloses a technology relating to a circuit board structure. The circuit board structure includes a plurality of parameter circuits in each of which an operation is specified by a parameter, a selection circuit that selects any one of the parameter circuits, and an output circuit that outputs a parameter included in the parameter circuit selected by the selection circuit. The plurality of parameter circuits include parameters different from each other for the respective parameter circuits. Therefore, the output circuit can output a different parameter by using a selected parameter circuit. In other words, a reception circuit that receives a parameter can receive a different parameter from the output circuit. PTL 1 is Japanese Laid-open Patent Publication No. 2008-046915.
PTL 2 discloses a technology relating to a control device and a method that control a power conversion device. PTL 2 discloses a technology for controlling a power conversion device to adjust, for example, the conversion efficiency to be a target conversion efficiency. PTL 2 is Japanese Laid-open Patent Publication No. 2006-020417.
PTL 1 merely describes that the parameter included in the parameter circuit selected by the selection circuit is output. In other words, PTL 1 neither considers reduction of power lost in a process of generating power nor mentions anything about this matter.
In the control device disclosed in PTL 2, DC power output from a DC power supply facility such as a solar photovoltaic system is converted to AC power by using a power conversion device. The control device determines a conversion efficiency of power in the power conversion device on the basis of the DC power output from the DC power supply facility and the AC power obtained by the conversion. The control device controls the power conversion device to adjust the determined conversion efficiency of power to be a target conversion efficiency. In this manner, the control device disclosed in PTL 2 corrects (hereinafter, described also as “post-correct”) the conversion efficiency on the basis of an output value output from the DC power supply facility. In other words, the control device corrects the conversion efficiency by using the above-described feedback method. Therefore, in PTL 2, it may be difficult to control the conversion efficiency to be a target conversion efficiency at an optimal timing. As a result, in PTL 2, it may be difficult to reduce the power loss in the power conversion device.
In this manner, in the method for optimizing the conversion efficiency of power in accordance with the state of output power, not only is it difficult to follow power consumed in the electronic device, but there is also a limit to reduction of power to be lost. In other words, it may be difficult to sufficiently produce a power reduction effect with this method.
A main object of the present invention is to provide a power supply device and the like capable of optimizing a conversion efficiency of power so as to be able to supply, in accordance with an operation status of a load that is a supply target of power, power necessary for the load.